Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

716
FXUS63 KLOT 281114
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
514 AM CST Wed Jan 28 2026

.KEY MESSAGES...

- Cold conditions will continue into the weekend with mainly
  subzero wind chills through Saturday morning.

- Threat for impactful lake effect snow continues to increase for
  northeast IL and northwest IN Thursday night through Saturday
  night.

&&

.DISCUSSION...
Issued at 236 AM CST Wed Jan 28 2026

Mainly quiet and cold conditions will prevail today. Longwave
troughing will remain entrenched across the Upper Midwest and
Great Lakes today, guiding a fast-moving disturbance well to our
south tonight into Thursday morning. West to northwesterly
breezes will develop this morning and afternoon which will
result in wind chills in the 10 to 20 below range this morning,
meandering towards 0 this afternoon. By later this afternoon and
overnight, expecting lake effect cloud cover to build westward
across the lake a bit as boundary layer flow turns a bit more
northwesterly. Have introduced some low precip chances for lake
effect snow showers across far northeastern portions of Porter
County tonight into early Thursday morning given progged
increases in 0-2 km BL moisture in this region which could
result in a dusting. The bulk of this LES will remain east of
the CWA, however. Thursday looks pretty similar to today, with
any lingering LES across NE Porter county ending through the
morning.

The main focus of this forecast remains squarely on the late
Thursday night through Sunday morning time frame with a long-
duration lake effect snow event looking increasing likely
across our lake adjacent counties. However, there are significant
uncertainties related to the specific evolution of this LES
episode, including the residence time of heavier rates with a
large amount of band movement and wobbling expected,
particularly in the initial stages through Friday night. This
has huge implications on snowfall totals, with the main axis of
persistent LES potentially setting up as far west as the NE
Illinois shore to as far east as northern Porter/La Porte
counties. The other consideration is what impact (if any)
increased ice concentration in the first dozen miles or so of
shore could have on lake fluxes, although based on Sunday`s
event at least, this may end up being a minimal impact. The
long-duration aspect of this event will also end up being
another issue, with many precip-free hours possible (a big
messaging challenge). Given all of this: while we ultimately may
need Winter Storm Watches for some or all of the lakeside
counties, there is too much uncertainty to justify issuance at
this time, especially considering the most organized/intense LES
may not develop until Friday evening into Saturday.


Early Friday Morning through Friday Afternoon:

There is fairly good model agreement in the handling of the
opening stages of this event late Thursday night/Friday morning
at least. The combination of a westward-advancing land breeze,
southward-pivoting upper low, and associated inverted surface
trough is expected to drive an initial region of snow across
northeast Illinois and parts of northwest Indiana on Friday
morning. This first stage will feature the coldest 850 mb
temperatures of the event, and resultantly the deepest lake-
induced equilibrium levels (near 10 kft) and associated CAPE,
but also likely the most transient and fast-moving features.
Latest guidance depicts at least a moderately intense region of
LES rolling ashore across NE Illinois, including the Chicago-
area) around or just after daybreak Friday morning. Suspect
given the degree of convergence and thermodynamics involved that
current coarse-resolution guidance is underdoing the amount of
QPF at this range, with the potential for one to two inch/hour
type rates with this initial activity and a high ratio/powdery
snow. Residence time of this first round may not be all that
long, however, potentially limiting the accums to start.
Another trend is towards more significant inland penetration
given the more cohesive convergence associated with the
aforementioned inverted trough and BL lapse rates increasing
markedly through the morning. Some of the current guidance
suggest a potential for robust snow showers or even bona fide
squall-like activity pushing west and southward through the area
into early afternoon. Have expanded PoPs across most of the
forecast area to account for this, although am not currently as
aggressive as some of the latest guidance would suggest
(NAM/GFS).


Friday Evening Through Saturday Night:

The main area of lake effect is forecast to gradually organize
into a single dominant band during this time, although may have
some difficulty doing so initially given modeled shear within
the lake boundary layer. However, surface convergence is
forecast to gradually focus down the long axis of the lake, with
ELs progged around 8-9 kft. The vast majority of guidance
indicates the main band shifting steadily away from NE Illinois
and across parts of NW Indiana Friday night/early Saturday
morning. Intermittent 1"+/hour rates will be possible, with
ratios likely to exceed 25:1. By Saturday morning, guidance
spread increases with the handling of the core of the main upper
low and orientation of the arctic high to our west, which in
turn results in a slightly different orientation to the
boundary-layer flow. GFS/CMC shift the flow NEly driving the
main lake band back across NE Illinois/Chicagoland, while the
rest of the global output more-or-less maintains a steady band
placement across the Lake-Porter-La Porte county vicinity. This
will be one of the main items to resolve over the coming
forecast shifts. If LES becomes quasistationary, some double-
digit snow totals would be in play.

Thermodynamic parameters will gradually become less supportive
of intense LES through Saturday evening/overnight, with activity
expected to gradually wane into Sunday morning.


Sunday night and beyond:

A very active upper pattern will continue next week with several
additional chances for snow, the first arriving Sunday night -
Monday, and another towards the middle/end of the week. By that
time, guidance does suggest a general warming trend, although
likely not enough to limit the wintry precip potential.

Carlaw

&&

.AVIATION /12Z TAFS THROUGH 18Z THURSDAY/...
Issued at 514 AM CST Wed Jan 28 2026

There are no significant aviation forecast concerns for the
current TAF period.

Westerly to northwesterly winds are expected over the course of
the TAF period, with occasional gusts to around 20 kts from
mid-morning through this afternoon. A few clouds based below
3000 ft AGL may be observed at times, along with some passing
higher clouds, but VFR conditions are expected to prevail
through the TAF period.

Ogorek

&&

.HYDROLOGY...
Issued at 230 PM CST Fri Jan 23 2026

River gauges, reports from local officials, and reports from
trained ice spotters continue to indicate a few ice jams across
the area due to the significant increase in river ice over
recent days. With continued cold weather into next week,
conditions will remain favorable for river ice formation. While
no widespread flooding is expected, localized ice jams may
occur.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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